MANUFACTURE OF ABSORBING SURFACE FOR SOLAR HEAT COLLECTOR

PURPOSE:To obtain an absorbing surface for a solar heat collector which is high in mechanical strength of a selective absorbing surface, by forming a thin layer of a solar heat absorbing substance obtained by adding silicon oxide or titanium oxide, on a substrate, and drying and heating it. CONSTITUTION:A thin layer having a high solar rays absorptance is formed by spraying a suspension containing manganese nitrate, etc. having a high solar rays absorptance, and silicon oxide or titanium oxide, on the surface of a substrate made of stainless steel, etc., or other method. When this thin layer is heated in the air after drying, manganese nitrate in the thin layer is changed chemically to black manganese oxide, and silicon oxide, etc. strongly couple generated manganese oxide particle each other, and between this particle and the substrate. Accordingly, by this method, it is possible to obtain a solar heat collector absorbing surface which is high not only a solar rays absorptance but also mechanical strength.